multiphysics.lab.asu.edu LAMMPS Workshop 2013 [email protected]Atomic scale investigation of grain boundary structure role on deformation and crack growth dynamics in Aluminum I. Adlakha 1 , K.N. Solanki 1 , M.A. Tschopp 2 1 School for Engineering of Matter, Transport, and Energy Arizona State University www.multiphysics.lab.asu.edu [email protected]2 Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21014. We acknowledge the support of the Office of Naval Research under grant N000141110793
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I. Adlakha 1, K.N. Solanki 1, M.A. Tschopp 2 1 School for Engineering of Matter, Transport, and Energy Arizona State University .
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Atomic scale investigation of grain boundary structure role on deformation and crack growth dynamics in Aluminum
I. Adlakha1, K.N. Solanki1, M.A. Tschopp2
1School for Engineering of Matter, Transport, and Energy
Arizona State University
www.multiphysics.lab.asu.edu [email protected] Research Laboratory, Weapons and Materials Research
Directorate, APG, MD 21014.
We acknowledge the support of the Office of Naval Research under grant N000141110793
The role of GB characteristics mentioned below on intergranular fracture Structural units (SUs) GB energy Initial free volume The slip plane orientation
relative to the crack plane and the growth direction.
The slip plane angle relative to the crack plane and the growth direction sufficient to describe the directional crack growth behavior and the ductile/brittle response.
A schematic of GB (Δz* = d - d0) free volume measurement
The maximum stress for GBs with ‘D’ or SF present, such as Σ13 (510) θ=22.6° and Σ97 (940) was lowest.
Σ97 (940) has 25% drop in maximum stress when compared to the Σ5 (210) The GB energy correlates to maximum stress of GBs, except for Σ97 (940) which has
The interface ahead of the crack tip underwent localized atomic shuffling.
The crack along the +X direction fails to nucleate a slip dislocation and grows in a brittle manner, in contrast the –X direction observes a slip nucleation around 3.25 % applied strain.
These events have been identified as the primary cause for the directional crack growth response observed.
Along most of the <110> GB interfaces, the crack growth was found to negligible with increased applied strain, with the exception to Σ27(552),Σ11(113) and Σ33(225) STGBs.
The Σ27(552) has substantial crack length on the right side (50), as compared to the left which has negligible maximum crack length (1).
The growth rates were found to be correlated to the initial free volume.
The incipient strain of the plastic event along each crack tips varied greatly. At the applied strain of 2.6%, an ISF was nucleated ahead of the crack tip along the +X direction; subsequently, a partial dislocation ( was nucleated from the ISF.
The amount of atomic movement ahead of the crack can be seen as negligible to accommodate plastic deformation.
Along the –X direction, a steady state crack growth was observed up to an applied strain of 3.5% .subsequently followed by nucleation of an ISF.
The growth along the –X direction between applied strains of 3.5-4.6% was retarded, primarily due to blunting of the crack tip and due to the high relative angle between the initial slip system and the crack plane (121.480) requiring a large amount of energy to propagate the dislocation .
The normal interface strength for GBs containing ‘D’ SU or SF in the GB structural description (Σ13 (510) θ=22.6° and Σ97 (940) θ=47.9°) showed noticeably lower interface strength compared to other <100> GBs.
The stress-strain response for the <110> STGB interface shows presence of two distinct regimes the ‘E’ SU GBs (ϕ > 109.47°) and the remaining GBs (ϕ < 109.47°).
Presence of ‘E’ SU lowers the maximum normal interface strength by an average 35% when compared to other <110> STGBs.
The maximum growth rate witnessed by the GB interface was in correlation with the initial free volume of the GB interface,
The orientation of slip planes relative to the crack plane and the growth direction were found to be a key aspect to inception of directional crack growth response.